When i put car i revers it reves high then stalls. and in drive it reves up and down

Lack of power and a vehicle running rough can be caused by one of two very common problems. One is a leak in the air duct between the air filter and the throttle body. This will generally make the car also hard to start. The other is a leak from rubber hoses connecting the intake to the PCV valve at the crankcase causing a vacuum leak. This will normally cause the vehicle to rev when in park and when first put in gear. More serious problems such as a misfire from a bad coil pack or a blown head gasket can also cause the vehicle to lose power and run poorly but these are not as common.